Flashing circuitry

ABSTRACT

Actuating a flashtube with circuitry which delivers a rapid succession of individual flash-producing pulses, and prevents further pulsing after the desired number of flashes. Preferably, capacitors are used to repeatedly store and discharge energy for firing the flash tube and timing the pulse cycles, in conjunction with SCR gating.

United States Patent [191 White et al.

[ Oct. 23, 1973 FLASHING CIRCUITRY [75] lnventors: Roby Byron White,Cumberland,

R.l.; Frederic Samuel Tobey, Hyde Park, Mass.

[73] Assignee: W. H. Brady Co., Milwaukee, Wis.

[22] Filed: July 11, 1972 [21] Appl. No.: 270,659

Related U.S. Application Data [63] Continuation-impart of Ser. No.122,930, March 10,

1971, abandoned.

[52] U.S. Cl 315/200 A, 315/238, 315/240,

315/241 R [51] Int. Cl. HOSb 37/00 [58] Field of Search 315/238, 240,241 R,

[56] References Cited UNITED STATES PATENTS 3,585,444 6/1971 Crowley315/240 Primary ExaminerRoy Lake Assistant Examiner-James B. MullinsAttorney-William W. Rymer, Jr.

[5 7] ABSTRACT Actuating a flashtube with circuitry which delivers arapid succession of individual flash-producing pulses, and preventsfurther pulsing after the desired number of flashes. Preferably,capacitors are used to repeatedly store and discharge energy for firingthe flash tube and timing the pulse cycles, in conjunction with SCRgating.

11 Claims, 4 Drawing Figures FLASHING CIRCUITRY CROSS-REFERENCE TORELATED APPLICATION This application is a continuation in part of ournow abandoned US. Pat. application Ser. No. 122,930, Flashing Circuitry,filed Mar. 10, 1971., the benefit of which filing date is hereinclaimed.

BACKGROUND OF THE INVENTION This invention relates to electricalcircuitry for delivering a series of flash-producing electrical pulsesto a flashtube in rapid succession.

SUMMARY OF THE INVENTION In general the invention features in one aspecta circuit comprising energy circuitry for receiving electrical energy ata first voltage, storing the energy at a second voltage higher than thefirst voltage, and repeatedly discharging the stored energy to initiatethe pulses, and timing circuitry to control the number of pulses in theseries. In another aspect the invention features a stepup transformerconnected to fire the flashtube, a first capacitor connected torepeatedly store up electrical energy and discharge into the primarywinding of the transformer, a gating element connected between the firstcapacitor and the primary winding to control the discharge, and a secondcapacitor connectedto store electrical energy while the first capacitoris storing the energy and to initiate actuation of the gating elementupon the charting of the second capacitor to a predetermined voltage,thereby to permit the discharge. In yet another aspect the inventionfeatures energy circuitry for receiving alternating current andrepeatedly storing and discharging electrical energy in flash cyclescorresponding to the cycles of the current, firing circuitry forreceiving during each flash cycle a portion of the energy discharged bythe energy circuitry and repeatedly firing the flashtube, and timingcircuitry for receiving during each cycle a portion of the energydischarged by the energy circuitry, accumulating the energy so received,and, when the energy so accumulated reaches a predetermined level,disabling the energy circuitry from further effectively dischargingenergy to the firing circuitry, whereby the series is terminated. Inpreferred embodiments the. energy circuitry includes a capacitor forstoring energy at the second voltage, lines arranged for receipt ofalternating current, a second capacitor connected to store the energy atvoltage rising to the first voltage during one portion of thealternating current cycle, and a gating element connected between thecapacitors, the voltage at the second capacitor rising to above thefirst voltage upon reversal of the alternating current during a secondportion of the cycle, the gating element during the second portion ofthe cycle permitting energy to flow from the second capacitor to thefirst mentioned capacitor, the second capacitor having a capacitancelarger than that of the first mentioned capacitor; the timing circuitryincludes a zener diode which limits receipt of energy from the energycircuitry to a peak voltage portion of each flash cycle, thereby toincrease the sensitivity of the timing circuitry to fluctuations in thevoltage level of the alternating current, a capacitor connected toreceive energy from the energy circuitry, and a gating element connectedto be actuated when that capacitor is charged to a predeterminedvoltage, the actuation of the gating element causing energy to be drawnfrom the energy circuitry to terminate the series of flashes; a resistoris connected between the timing and energy circuitries to limit theenergy level increase per cycle in the timing circuitry, thereby ,todetermine the number of the pulses in the series; a switch is providedto discharge the capacitor in the timing circuitry at the termination ofeach series of flashes, so that in each subsequent series approximatelythe same total energy will be delivered to the flashtube; and an SCR isconnected as a gate to control the storage of electrical energy in theenergy circuitry, elements being connected with the timing circuitry tomaintain the SCR in an off condition upon termination of each series offlashes. Also, in preferred embodiments, a thermistor is mounted in heattransfer relationship with a capacitor so as to provide decreasedresistance as the capacitor heats up, to counteract the characteristicof the warmer capacitor to deliver more energy per pulse.

The invention thus achieves reliable and accurate control of the numberand energy level of the flashproducing pulses, and keeps approximatelyconstant the total energy delivered to the flashtube per series offlashes, even when line voltage fluctuates, all with a minimum ofcircuit elements.

Other features and advantages of the invention will be apparent from thefollowing description of the preferred embodiment thereof, takentogether with the drawings. 1

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofa fragment of the processor;

FIG. 2 is an enlargement of a fragment of a tape cartridge of widthdifferent from that shown in FIG. 1;

FIG. 3 is a sectional view taken at to the section of FIG. 1; and

FIG. 4 is a schematic drawing of electrical circuitry for pulsing theflashtube.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, labelmaking apparatus is shown in which a circular master stencil 10 ismounted between xenon arc flashtube 12 and cartridge 14 of ultravioletimaging tape 16(coated with a material sold by E. I. duPont de Nemoursunderthe trade designation Dylux). The cartridge is of opaque plastic,has a side wall 18 from which protrude three identical exterior lugs 20,and has a tape guide 22 of inside width barely larger than the width ofthe tape. Secured to mounting bracket 24 is a post 26 which fits throughopening 28 to support the cartridge with lugs 20 against bracket wallsurface 30. The lugs are equally spaced angularly about opening 28 tovertically orient the cartridge, and are kept in contact with surface 20by springs 32 on post 26.

Knurled tape indexing wheel 40 is carried by shaft 42 and pressesagainst tape 16 through opening 44 in guide 22. A back-up tab 46 ofTeflon is fixed to the inner guide surface opposite opening 44, to allowtape 16 to slide smoothly through the guide as wheel 40 rotates. Fingeroperated lever 48 is provided to rotate shaft 42 through conventionallinkage (not shown).

Tape 16 extends from guide 22 to an imaging station 50 beneath aperture52 at the bottom of flashtube housing 54. Filter v56 covers aperture 52to screen out all light except that in the ultraviolet frequency range.

Stencil 10 is opaque except for characters (e.g., at 58) arranged alongits periphery. The stencil can be rotated about axis 60 to bring aselected character into registry with flashtube 12.

An electrical circuit (shown in detail in FIG. 4), including switch 70mounted beneath lever 48 of the index mechanism, is arranged to supplyto flashtube 12, upon each actuation of switch 70, a rapid series (overa total period of about 400 milliseconds) of 25 electrical pulses eachof 1.56 joules energy level (less than 5 percent of explosion energy)and 200 microseconds duration.

The cartridge shown in FIG. 2 is identical to thatof FIGS. 1 and 3except that guide 22' is wider than guide 22 (to accommodate a widertape, omitted from FIG. 2), and lugs 20' are correspondingly shorter, sothat the distance X between the ends of the lugs and the centerline ofthe tape guide is the same for all cartridges.

In use, a cartridge with tape of the desired width is loaded on post 26.With lugs 20 or 20' against surface 30, the centerline of guide 22 or22' are hence the centerline of the tape, will be centered underaperture 52, whatever the width of the tape. To make a label, stencil(or imaging master) is rotated to bring the desired character to imagingstation 50, and lever 48 is depressed to close switch 70, causingflashtube 12 to flash 25 times as the 25 pulses described above aredelivered. After exposure, lever 48 is released, rotating wheel 40 toadvance tape 16. (Or, the tape can be advanced prior to imaging.)Successive characters are similarly imaged on the tape. Upon exposure tovisible light the images on the tape become photographically fixed.

The low energy level (relative to explosion energy) pulsing of the tubeprevents crazing, or extreme darkening of the flashtube envelope, orpressure loss, over a tube life of often millions of flashes, eventhough the total energy supplied in the serires of flashes which make upeach character exposure equals a large fraction of explosion energy andthe flashes follow each other so rapidly that most of the heat generatedby each flash is still present in the tube when the succeeding flashoccurs. At the same time, the total energy level of each characterexposure is sufficient to give a dark image.

Image darkness can be controlled by varying the number of flashes perexposure.

The electrical circuitry for actuating the flashtube is shown in FIG. 4,and in general consists of a main energy circuit 100 for providing aseries of flashes, timed in accordance with the frequency (50-60 B2) ofthe AC line current applied through lines 102 and 104, a firing circuit106 for firing the flashtube under the control of circuit 100, and atotal cycle timing circuit 108 for terminating the series of flashesafter the flashtube has fired the desired number of times.

In circuit 100, electrolytic capacitor 110 (60 mfd) is charged duringeach AC cycle, which provices the energy to trigger circuit 106. Inparticular, when switch 70 (single pole double throw) is depressed (asshown in FIG. 4) line current charges capacitor 112 (400 mfd) to nearpeak line voltage through resistor 114 (10 Ohm) and diode 1 16 duringthe first quarter of the AC cycle. During the second and third quartersof the AC cycle the voltage at junction 118 rises to approximately twicepeak voltage (the sum of the reversed line voltage and that alreadypresent across capacitor 112), SCR

120 is turned on (and is kept on by 10K resistor 122), and a portion ofthe charge on capacitor 112 transfers to capacitor 110 (the ratio ofcharges of the two capacitors being in inverse proportion to the ratioof capacitances, so that the smaller capacitor 110 will be charged toabove peak line voltage). Resistors 125 (K) and 126 (220K) are bleedresistors to discharge capacitors 120 and for safety purposes when theunit is turned off. Resistor 128 (2.2K) and diode 130 work inconjunction with circuit 108 as described below.

While capacitor 110 is being charged as just described it in turncharges, in circuit 106, capacitor 132 (0.33 mfd) through resistor 134(3.3K), and capacitor 136 (0.022 mfd) through resistor 138 (1.2 meg).When charged to approximately 70 volts, capacitor 136 fires neon tube140, turning on SCR 142. As a result, capacitor 132 discharges into theprimary of stepup transformer 144. The voltage across the transformersecondary then fires flashtube 12. The current through the flashtubecauses SCR 142 to be reset. Ground reference resistor 146 (1K) preventsfalse firing of SCR 142.

During each flash-producing discharge of capacitor 110 current alsoflows through diode 130, resistor 150 (220 Ohms), diode 152, thermistor153, zener diode 154 (V), and resistor 156 (chosen to give the desiredcharging rate of capacitor 158, and hence the desired number of flashesper exposure) to charge capacitor 158 (0.1 mfd). Diode 152 preventscurrent leak from capacitor 158 between flashes, so that the voltageacross capacitor 158 increases upon each flash, and eventually firesneon tube 160, turning on SCR 162 and causing discharge of capacitor110, terminating the series of flashes. The voltage drop across diodecauses SCR 120 to turn off, and the continuing current flow throughresistor 128 and diode 130 from capacitor 112 holds SCR 120 in its offcondition. Resistor 156 controls the rate of charge of capacitor 158,hence determining the number of flashes per exposure. Zener diode 154provides a threshhold voltage below which current will not flow tocapacitor 158, so that capacitor 158 charges during only a small peakportion of each AC cycle. As a result, the charge rate of capacitor 158is sensitive to fluctuations in line voltage, so that the number offlashes per exposure will dropas line voltage increases, tending toequalize total energy supplied to the flashtube per exposure.

The thermistor 153 compensates for the fact that, even at unchangingline voltage, more energy is delivered per pulse as the components, inparticular the capacitors 110 and 112, warm up. The thermistor 153,which is mounted in heat transfer relationship with capacitor 110,provides decreased resistance as capacitor 110 heats up, this chargingcapacitor 158 a greater amount on each pulse, and thus diminishing thenumber of pulses in a way compensating for the increased energy perpulse owing to temperature increase.

Resistor 164 (1K) and capacitor 166 (0.047 mfd) prevent false firing ofSCR 162.

When switch 70 is released capacitor 158 is discharged by the normallyclosed contacts of switch 70, so that the next exposure cycle will be ofthe same length.

Subject matter disclosed herein relating to positioning the cartridgeand to the low friction back-up tab was the sole invention of FredericS. Tobey.

cycles a portion of said energy discharged by said energy circuit means,accumulating energy so received, and, when said energy so accumulatedreaches a predetermined level, disabling said energy circuit means fromfurther effectively discharging energy to said firing circuit means toterminate said series,

' said energy circuit means being connected to receive said alternatingcurrent from a said source of the same and being connected to saidfiring circuit means and said timing circuit means for delivery ofenergy from said energy circuit means to said firing circuit means andsaid timing circuit means,

said timing circuit means comprising a first capacitor connected toreceive energy from said energy circuit means and a gating elementconnected to be actuated to cause said disabling thus to terminate saidseries when said capacitor is charged to a predetermined voltage, and

said energy circuit means comprising a second capacitor connected tostore in said energy circuit means said energy from said source of saidalternating current,

said timing circuit means being connected to draw energy from saidsecond capacitor upon actuation of said gating element.

2. The circuit of claim 1 in which said energy circuit means includes athird capacitor, said third capacitor having a capacitance greater thansaid capacitor and being connected therewith to supply energy thereto tocharge said second capacitor to a voltage higher than the voltage ofsaid source.

3. The circuit of claim 2 in which a second gating element is connectedbetween said second capacitor and said third capacitor, said secondgating element during a second portion of said cycles permitting energyto flow from said third capacitor to said second capacitor.

4. The circuit of claim 1 which includes in said firing circuit means astep-up transformer connected to fire said flashtube, a second gatingelement between a third capacitor and a primary winding of saidtransformer, and a fourth capacitor connected to store energy while saidfirst capacitor is storing energy, to initiate actuation of said secondgating element upon the charging of said fourth capacitor to apredetermined voltage.

5. The circuit of claim 4 in which said fourth capacitor is connected inseries with a neon tube, and said second gating element is an SCRconnected to be turned on upon the breakdown of said neon tube when saidfourth capacitor is charged to said predetermined voltage.

6. The circuit of claim 1 wherein said timing circuitry includes anelement which limits receipt of energy from said energy circuitry to apeak voltage portion of each said flash cycle, thereby to increase thesensitivity of said timing circuitry to fluctuations in the voltagelevel of said alternating current.

7. The circuit of claim 6 wherein said element is a zener diode.

8. The circuit of claim 1 which includes a switch to discharge saidfirst capacitor to terminate said series.

9. The circuit of claim 1 in which said timing circuit means includes athermistor electrically connected for passage therethrough of saidenergy discharged by said energy circuit means, said thermistor beingmounted in heat transfer relationship with said second capacitor.

10. An electrical circuit for delivering to a flashtube a series offlash-producing electrical pulses in rapid succession, comprising:

energy circuit means for repeatedly storing and discharging electricalenergy in flash cycles corresponding to the cycles of an alternatingcurrent source, firing circuit means for receiving during each of saidflash cycles a portion of said energy discharged by said energy circuitmeans and repeatedly firing said flashtube, timing circuit means forreceiving during each of said cycles a portion of said energy dischargedby said energy circuit means, accumulating energy so received, and, whensaid energy so accumulated reaches a predetermined level, disabling saidenergy circuit means from further effectively discharging energy to saidfiring circuit means to terminate said series, said energyv circuitmeans being connected to receive said alternating current from a saidsource of the same and being connected to said firing circuit means andsaid timing circuit means for delivery of energy from said energycircuit means to said firing circuit means and said timing circuitmeans, said timing circuit means comprising a resistor connected betweensaid energy circuit means and portions of said timing circuit means tolimit energy level increase per cycle in said timing circuit means,thereby to determine the number of said pulses in said series. I 11. Anelectrical circuit for delivering to a flashtube a series offlash-producing electrical pulses in rapid succession, comprising: Q

energy circuit means for repeatedly storing and discharging electricalenergy in flash cycles corresponding to the cycles of an alternatingcurrent source, firing circuit means for receiving during each of saidflash cycles a portion of said energy discharged by said energy circuitmeans and repeatedly firing said flashtube, timing circuit means forreceiving during each of said cycles a portion of said energy dischargedby said energy circuit means, accumulating energy so received, and, whensaid energy so accumulated reaches a predetermined level, disabling saidenergy circuit means from further effectively discharging energy to saidfiring circuit means to terminate said series, said energy circuit meansbeing connected to receive said alternating current from a said sourceof the same and being connected to said firing circuit means and saidtiming circuit means for delivery of energy from said energy circuitmeans to said firing circuit means and said timing circuit means, saidtiming circuit means comprising a capacitor connected to receive saidenergy from said energy circuit means and a switch to discharge saidcapacitor to terminate said series.

1. An electrical circuit for delivering to a flashtube a series offlash-producing electrical pulses in rapid succession, comprising:energy circuit means for repeatedly storing and discharging electricalenergy in flash cycles corresponding to the cycles of an alternatingcurrent source, firing circuit means for receiving during each of saidflash cycles a portion of said energy discharged by said energy circuitmeans and repeatedly firing said flashtube, timing circuit means forreceiving during each of said cycles a portion of said energy dischargedby said energy circuit means, accumulating energy so received, and, whensaid energy so accumulated reaches a predetermined level, disabling saidenergy circuit means from further effectively discharging energy to saidfiring circuit means to terminate said series, said energy circuit meansbeing connected to receive said alternating current from a said sourceof the same and being connected to said firing circuit means and saidtiming circuit means for delivery of energy from said energy circuitmeans to said firing circuit means and said timing circuit means, saidtiming circuit means comprising a first capacitor connected to receiveenergy from said energy circuit means and a gating element connected tobe actuated to cause said disabling thus to terminate said series whensaid capacitor is charged to a predetermined voltAge, and said energycircuit means comprising a second capacitor connected to store in saidenergy circuit means said energy from said source of said alternatingcurrent, said timing circuit means being connected to draw energy fromsaid second capacitor upon actuation of said gating element.
 2. Thecircuit of claim 1 in which said energy circuit means includes a thirdcapacitor, said third capacitor having a capacitance greater than saidcapacitor and being connected therewith to supply energy thereto tocharge said second capacitor to a voltage higher than the voltage ofsaid source.
 3. The circuit of claim 2 in which a second gating elementis connected between said second capacitor and said third capacitor,said second gating element during a second portion of said cyclespermitting energy to flow from said third capacitor to said secondcapacitor.
 4. The circuit of claim 1 which includes in said firingcircuit means a step-up transformer connected to fire said flashtube, asecond gating element between a third capacitor and a primary winding ofsaid transformer, and a fourth capacitor connected to store energy whilesaid first capacitor is storing energy, to initiate actuation of saidsecond gating element upon the charging of said fourth capacitor to apredetermined voltage.
 5. The circuit of claim 4 in which said fourthcapacitor is connected in series with a neon tube, and said secondgating element is an SCR connected to be turned on upon the breakdown ofsaid neon tube when said fourth capacitor is charged to saidpredetermined voltage.
 6. The circuit of claim 1 wherein said timingcircuitry includes an element which limits receipt of energy from saidenergy circuitry to a peak voltage portion of each said flash cycle,thereby to increase the sensitivity of said timing circuitry tofluctuations in the voltage level of said alternating current.
 7. Thecircuit of claim 6 wherein said element is a zener diode.
 8. The circuitof claim 1 which includes a switch to discharge said first capacitor toterminate said series.
 9. The circuit of claim 1 in which said timingcircuit means includes a thermistor electrically connected for passagetherethrough of said energy discharged by said energy circuit means,said thermistor being mounted in heat transfer relationship with saidsecond capacitor.
 10. An electrical circuit for delivering to aflashtube a series of flash-producing electrical pulses in rapidsuccession, comprising: energy circuit means for repeatedly storing anddischarging electrical energy in flash cycles corresponding to thecycles of an alternating current source, firing circuit means forreceiving during each of said flash cycles a portion of said energydischarged by said energy circuit means and repeatedly firing saidflashtube, timing circuit means for receiving during each of said cyclesa portion of said energy discharged by said energy circuit means,accumulating energy so received, and, when said energy so accumulatedreaches a predetermined level, disabling said energy circuit means fromfurther effectively discharging energy to said firing circuit means toterminate said series, said energy circuit means being connected toreceive said alternating current from a said source of the same andbeing connected to said firing circuit means and said timing circuitmeans for delivery of energy from said energy circuit means to saidfiring circuit means and said timing circuit means, said timing circuitmeans comprising a resistor connected between said energy circuit meansand portions of said timing circuit means to limit energy level increaseper cycle in said timing circuit means, thereby to determine the numberof said pulses in said series.
 11. An electrical circuit for deliveringto a flashtube a series of flash-producing electrical pulses in rapidsuccession, comprising: energy circuit means for repeatedly storing anddischarging electrical energy in flash cycles corresponding to thecyCles of an alternating current source, firing circuit means forreceiving during each of said flash cycles a portion of said energydischarged by said energy circuit means and repeatedly firing saidflashtube, timing circuit means for receiving during each of said cyclesa portion of said energy discharged by said energy circuit means,accumulating energy so received, and, when said energy so accumulatedreaches a predetermined level, disabling said energy circuit means fromfurther effectively discharging energy to said firing circuit means toterminate said series, said energy circuit means being connected toreceive said alternating current from a said source of the same andbeing connected to said firing circuit means and said timing circuitmeans for delivery of energy from said energy circuit means to saidfiring circuit means and said timing circuit means, said timing circuitmeans comprising a capacitor connected to receive said energy from saidenergy circuit means and a switch to discharge said capacitor toterminate said series.